There are now so many roads dissecting the Earth that, despite over 80 percent of land being relatively undisturbed, this has been cut up into 600,000 fragments. These fragments are generally too small to hold significant populations of wildlife, threatening the survival of many species.

This latest report, published in Science, warns that the uncontrolled construction of roads is a very real threat to the world’s biodiversity, as they increase pollution, destroy ecosystems, and shatter animal populations.

In fact, the researchers found that there are so many roads now crisscrossing the planet’s surface and fragmenting the landscape, that only 7 percent of patches of land created by roads are larger than 100 square kilometers (38 square miles). This dramatically highlights the impact that our infrastructure has on the environment, pushing wildlife away from human habitation.

 ^{Ibisch et al. 2016}

The problems that road building cause for wildlife are multi-faceted. There is the initial destruction of the environment to create the roads, for which land is torn up and trees felled. Then there is the fragmentation of the habitat, which as the results from this latest study show are massively significant. This can isolate populations of animals, preventing them from migrating or traveling in the search of food or mates. It also increases the risk that they will be hit by cars and traffic as they roam for resources.

But it also opens up once remote regions for hunting. One of the main issues surrounding mining and forestry, particularly in the tropics, is that the roads created to service these industries effectively opens up arteries into the heart of forests and landscape where it was once difficult to reach. This allows poachers to infiltrate the forests, and enables them to access animal populations once thought to be safe.

It is not only large animals, like elephants, that feel the brunt either. One study on birds in the Amazon found that the more roads there were in a region, the fewer the species of birds. The creation of roads can play their own specific role in reducing biodiversity, altering the flow of water through an ecosystem, changing the amount of light that reaches the forest floor, or stopping species' movements. This latest study found that the impact of roads on the environment was felt for an average of 1 kilometer (0.6 miles) either side of the road.